A 62-year-old dairy farmer has two months of low-grade fever, night sweats and weight loss. Three separate blood cultures are negative. Transoesophageal echocardiography shows an aortic valve vegetation. Serology shows phase I IgG antibodies to Coxiella burnetii at a titre of 1:2048. What is the diagnosis?
- A Brucella melitensis endocarditis
- B Q fever chronic endocarditis ✓
- C Non-bacterial thrombotic (marantic) endocarditis
- D Libman-Sacks endocarditis
Correct answer: B. Q fever chronic endocarditis
Explanation
Chronic Q fever endocarditis is one of the classic culture-negative endocarditises and typically affects patients exposed to livestock. Diagnosis rests on serology, with a phase I IgG titre above 1:800 considered diagnostic in the appropriate setting; Coxiella does not grow in routine blood cultures. Marantic endocarditis produces sterile platelet-fibrin vegetations in malignancy or hypercoagulable states, while Libman-Sacks lesions occur in lupus and antiphospholipid syndrome.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.